Radio Energy Harvested With Inkjet-Printed Antenna

judgecorp writes "Everlasting green energy for RF tags and other low-power devices could be possible as scientists have harvested energy from ambient radio waves using cheap antennas printed by an ordinary inkjet. The scientists, from Georgia Tech, started at 100MHz but have now produced systems which scavenge power at up to 60GHz, allowing them to draw power from most of today's major radio technologies."

Comments

radio harvested with piece of rock (galena)

[YesIAmAScript]

It's called a crystal radio.

A diode does it too.

Re:So they're using background radiation only?

[icebike]

Because it seems like if you want to power these things, they need to use power from a radio source. Which doesn't make them green at all.

The radio source is there all the time anyway, It is there for other uses.

But as should be obvious, the vast majority of radio waves are never used, being disparate over vast distances or absorbed by the earth itself. Utilizing this "wasted" energy costs nothing, because we are already emitting that energy, and utilizing it costs no more. At the emitter you can't measure if a radio wave hits one antenna or a million antennas. Its no different to you as the sender of that wave.

So by using freely available wasted energy these devices obviate the need for ANOTHER power source and are therefor green.

Re:IANARS, but...

[Tacvek]

It will degrade the signal of downstream recipients. So does absolutely every radio receiver, with no exceptions.
However, please consider that the only downstream recipient may well be the earth or space, considering that the path between a transmitter and receiver often does not pass particularly close to another receiver. How much one of these would impact the downstream signal quality anyway depends on just how much power this is extracting, and just how weak the signal would have been at the downstream receiver without this being present.

Also keep in mind that radio waves can be rather fickle. Placing these devices in certain locations may actually increase the received signal strength downstream, perhaps by absorbing an interference source, or by attenuating a secondary path of the signal which would have interfered with the primary signal.